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Revision 1.7 by root, Sat Nov 3 16:25:49 2007 UTC vs.
Revision 1.18 by root, Tue Dec 11 21:18:25 2007 UTC

… …
9 9
10 my $w = EV::timer 2, 0, sub { 10 my $w = EV::timer 2, 0, sub {
11 warn "is called after 2s"; 11 warn "is called after 2s";
12 }; 12 };
13 13
14 my $w = EV::timer 2, 1, sub { 14 my $w = EV::timer 2, 2, sub {
15 warn "is called roughly every 2s (repeat = 1)"; 15 warn "is called roughly every 2s (repeat = 2)";
16 }; 16 };
17 17
18 undef $w; # destroy event watcher again 18 undef $w; # destroy event watcher again
19 19
20 my $w = EV::periodic 0, 60, sub { 20 my $w = EV::periodic 0, 60, 0, sub {
21 warn "is called every minute, on the minute, exactly"; 21 warn "is called every minute, on the minute, exactly";
22 }; 22 };
23 23
24 # IO 24 # IO
25 25
26 my $w = EV::io *STDIN, EV::READ, sub { 26 my $w = EV::io *STDIN, EV::READ, sub {
27 my ($w, $revents) = @_; # all callbacks get the watcher object and event mask 27 my ($w, $revents) = @_; # all callbacks receive the watcher and event mask
28 warn "stdin is readable, you entered: ", <STDIN>; 28 warn "stdin is readable, you entered: ", <STDIN>;
29 }; 29 };
30 30
31 # SIGNALS 31 # SIGNALS
32 32
33 my $w = EV::signal 'QUIT', sub { 33 my $w = EV::signal 'QUIT', sub {
34 warn "sigquit received\n"; 34 warn "sigquit received\n";
35 }; 35 };
36 36
37 my $w = EV::signal 3, sub {
38 warn "sigquit received (this is GNU/Linux, right?)\n";
39 };
40
41 # CHILD/PID STATUS CHANGES 37 # CHILD/PID STATUS CHANGES
42 38
43 my $w = EV::child 666, sub { 39 my $w = EV::child 666, sub {
44 my ($w, $revents) = @_; 40 my ($w, $revents) = @_;
45 # my $pid = $w->rpid;
46 my $status = $w->rstatus; 41 my $status = $w->rstatus;
47 }; 42 };
43
44 # STAT CHANGES
45 my $w = EV::stat "/etc/passwd", 10, sub {
46 my ($w, $revents) = @_;
47 warn $w->path, " has changed somehow.\n";
48 };
48 49
49 # MAINLOOP 50 # MAINLOOP
50 EV::loop; # loop until EV::loop_done is called 51 EV::loop; # loop until EV::unloop is called or all watchers stop
51 EV::loop EV::LOOP_ONESHOT; # block until at least one event could be handled 52 EV::loop EV::LOOP_ONESHOT; # block until at least one event could be handled
52 EV::loop EV::LOOP_NONBLOCK; # try to handle same events, but do not block 53 EV::loop EV::LOOP_NONBLOCK; # try to handle same events, but do not block
53 54
54DESCRIPTION 55DESCRIPTION
55 This module provides an interface to libev 56 This module provides an interface to libev
56 (<http://software.schmorp.de/pkg/libev.html>). 57 (<http://software.schmorp.de/pkg/libev.html>). While the documentation
58 below is comprehensive, one might also consult the documentation of
59 libev itself (<http://cvs.schmorp.de/libev/ev.html>) for more subtle
60 details on watcher semantics or some discussion on the available
61 backends, or how to force a specific backend with "LIBEV_FLAGS", or just
62 about in any case because it has much more detailed information.
57 63
58BASIC INTERFACE 64BASIC INTERFACE
59 $EV::DIED 65 $EV::DIED
60 Must contain a reference to a function that is called when a 66 Must contain a reference to a function that is called when a
61 callback throws an exception (with $@ containing thr error). The 67 callback throws an exception (with $@ containing the error). The
62 default prints an informative message and continues. 68 default prints an informative message and continues.
63 69
64 If this callback throws an exception it will be silently ignored. 70 If this callback throws an exception it will be silently ignored.
65 71
66 $time = EV::time 72 $time = EV::time
… …
69 $time = EV::now 75 $time = EV::now
70 Returns the time the last event loop iteration has been started. 76 Returns the time the last event loop iteration has been started.
71 This is the time that (relative) timers are based on, and refering 77 This is the time that (relative) timers are based on, and refering
72 to it is usually faster then calling EV::time. 78 to it is usually faster then calling EV::time.
73 79
74 $method = EV::ev_method 80 $method = EV::method
75 Returns an integer describing the backend used by libev 81 Returns an integer describing the backend used by libev
76 (EV::METHOD_SELECT or EV::METHOD_EPOLL). 82 (EV::METHOD_SELECT or EV::METHOD_EPOLL).
77 83
78 EV::loop [$flags] 84 EV::loop [$flags]
79 Begin checking for events and calling callbacks. It returns when a 85 Begin checking for events and calling callbacks. It returns when a
80 callback calls EV::loop_done. 86 callback calls EV::unloop.
81 87
82 The $flags argument can be one of the following: 88 The $flags argument can be one of the following:
83 89
84 0 as above 90 0 as above
85 EV::LOOP_ONESHOT block at most once (wait, but do not loop) 91 EV::LOOP_ONESHOT block at most once (wait, but do not loop)
86 EV::LOOP_NONBLOCK do not block at all (fetch/handle events but do not wait) 92 EV::LOOP_NONBLOCK do not block at all (fetch/handle events but do not wait)
87 93
88 EV::loop_done [$how] 94 EV::unloop [$how]
89 When called with no arguments or an argument of 1, makes the 95 When called with no arguments or an argument of EV::UNLOOP_ONE,
90 innermost call to EV::loop return. 96 makes the innermost call to EV::loop return.
91 97
92 When called with an agrument of 2, all calls to EV::loop will return 98 When called with an argument of EV::UNLOOP_ALL, all calls to
93 as fast as possible. 99 EV::loop will return as fast as possible.
94 100
95 WATCHER 101 $count = EV::loop_count
102 Return the number of times the event loop has polled for new events.
103 Sometiems useful as a generation counter.
104
105 EV::once $fh_or_undef, $events, $timeout, $cb->($revents)
106 This function rolls together an I/O and a timer watcher for a single
107 one-shot event without the need for managing a watcher object.
108
109 If $fh_or_undef is a filehandle or file descriptor, then $events
110 must be a bitset containing either "EV::READ", "EV::WRITE" or
111 "EV::READ | EV::WRITE", indicating the type of I/O event you want to
112 wait for. If you do not want to wait for some I/O event, specify
113 "undef" for $fh_or_undef and 0 for $events).
114
115 If timeout is "undef" or negative, then there will be no timeout.
116 Otherwise a EV::timer with this value will be started.
117
118 When an error occurs or either the timeout or I/O watcher triggers,
119 then the callback will be called with the received event set (in
120 general you can expect it to be a combination of "EV:ERROR",
121 "EV::READ", "EV::WRITE" and "EV::TIMEOUT").
122
123 EV::once doesn't return anything: the watchers stay active till
124 either of them triggers, then they will be stopped and freed, and
125 the callback invoked.
126
127 EV::feed_fd_event ($fd, $revents)
128 Feed an event on a file descriptor into EV. EV will react to this
129 call as if the readyness notifications specified by $revents (a
130 combination of "EV::READ" and "EV::WRITE") happened on the file
131 descriptor $fd.
132
133 EV::feed_signal_event ($signal)
134 Feed a signal event into EV. EV will react to this call as if the
135 signal specified by $signal had occured.
136
137 WATCHER OBJECTS
96 A watcher is an object that gets created to record your interest in some 138 A watcher is an object that gets created to record your interest in some
97 event. For instance, if you want to wait for STDIN to become readable, 139 event. For instance, if you want to wait for STDIN to become readable,
98 you would create an EV::io watcher for that: 140 you would create an EV::io watcher for that:
99 141
100 my $watcher = EV::io *STDIN, EV::READ, sub { 142 my $watcher = EV::io *STDIN, EV::READ, sub {
… …
108 received events. 150 received events.
109 151
110 Each watcher type has its associated bit in revents, so you can use the 152 Each watcher type has its associated bit in revents, so you can use the
111 same callback for multiple watchers. The event mask is named after the 153 same callback for multiple watchers. The event mask is named after the
112 type, i..e. EV::child sets EV::CHILD, EV::prepare sets EV::PREPARE, 154 type, i..e. EV::child sets EV::CHILD, EV::prepare sets EV::PREPARE,
113 EV::periodic sets EV::PERIODIC and so on, with the exception of IO 155 EV::periodic sets EV::PERIODIC and so on, with the exception of I/O
114 events (which can set both EV::READ and EV::WRITE bits), and EV::timer 156 events (which can set both EV::READ and EV::WRITE bits), and EV::timer
115 (which uses EV::TIMEOUT). 157 (which uses EV::TIMEOUT).
116 158
117 In the rare case where one wants to create a watcher but not start it at 159 In the rare case where one wants to create a watcher but not start it at
118 the same time, each constructor has a variant with a trailing "_ns" in 160 the same time, each constructor has a variant with a trailing "_ns" in
… …
124 166
125 Also, all methods changing some aspect of a watcher (->set, ->priority, 167 Also, all methods changing some aspect of a watcher (->set, ->priority,
126 ->fh and so on) automatically stop and start it again if it is active, 168 ->fh and so on) automatically stop and start it again if it is active,
127 which means pending events get lost. 169 which means pending events get lost.
128 170
129 WATCHER TYPES 171 COMMON WATCHER METHODS
130 Now lets move to the existing watcher types and asociated methods. 172 This section lists methods common to all watchers.
131
132 The following methods are available for all watchers. Then followes a
133 description of each watcher constructor (EV::io, EV::timer,
134 EV::periodic, EV::signal, EV::child, EV::idle, EV::prepare and
135 EV::check), followed by any type-specific methods (if any).
136 173
137 $w->start 174 $w->start
138 Starts a watcher if it isn't active already. Does nothing to an 175 Starts a watcher if it isn't active already. Does nothing to an
139 already active watcher. By default, all watchers start out in the 176 already active watcher. By default, all watchers start out in the
140 active state (see the description of the "_ns" variants if you need 177 active state (see the description of the "_ns" variants if you need
141 stopped watchers). 178 stopped watchers).
142 179
143 $w->stop 180 $w->stop
144 Stop a watcher if it is active. Also clear any pending events 181 Stop a watcher if it is active. Also clear any pending events
145 (events that have been received but that didn't yet result in a 182 (events that have been received but that didn't yet result in a
146 callback invocation), regardless of wether the watcher was active or 183 callback invocation), regardless of whether the watcher was active
147 not. 184 or not.
148 185
149 $bool = $w->is_active 186 $bool = $w->is_active
150 Returns true if the watcher is active, false otherwise. 187 Returns true if the watcher is active, false otherwise.
188
189 $current_data = $w->data
190 $old_data = $w->data ($new_data)
191 Queries a freely usable data scalar on the watcher and optionally
192 changes it. This is a way to associate custom data with a watcher:
193
194 my $w = EV::timer 60, 0, sub {
195 warn $_[0]->data;
196 };
197 $w->data ("print me!");
151 198
152 $current_cb = $w->cb 199 $current_cb = $w->cb
153 $old_cb = $w->cb ($new_cb) 200 $old_cb = $w->cb ($new_cb)
154 Queries the callback on the watcher and optionally changes it. You 201 Queries the callback on the watcher and optionally changes it. You
155 can do this at any time without the watcher restarting. 202 can do this at any time without the watcher restarting.
… …
160 Pending watchers with higher priority will be invoked first. The 207 Pending watchers with higher priority will be invoked first. The
161 valid range of priorities lies between EV::MAXPRI (default 2) and 208 valid range of priorities lies between EV::MAXPRI (default 2) and
162 EV::MINPRI (default -2). If the priority is outside this range it 209 EV::MINPRI (default -2). If the priority is outside this range it
163 will automatically be normalised to the nearest valid priority. 210 will automatically be normalised to the nearest valid priority.
164 211
165 The default priority of any newly-created weatcher is 0. 212 The default priority of any newly-created watcher is 0.
166 213
214 Note that the priority semantics have not yet been fleshed out and
215 are subject to almost certain change.
216
167 $w->trigger ($revents) 217 $w->invoke ($revents)
168 Call the callback *now* with the given event mask. 218 Call the callback *now* with the given event mask.
169 219
220 $w->feed_event ($revents)
221 Feed some events on this watcher into EV. EV will react to this call
222 as if the watcher had received the given $revents mask.
223
224 $revents = $w->clear_pending
225 If the watcher is pending, this function returns clears its pending
226 status and returns its $revents bitset (as if its callback was
227 invoked). If the watcher isn't pending it does nothing and returns
228 0.
229
230 $previous_state = $w->keepalive ($bool)
231 Normally, "EV::loop" will return when there are no active watchers
232 (which is a "deadlock" because no progress can be made anymore).
233 This is convinient because it allows you to start your watchers (and
234 your jobs), call "EV::loop" once and when it returns you know that
235 all your jobs are finished (or they forgot to register some watchers
236 for their task :).
237
238 Sometimes, however, this gets in your way, for example when you the
239 module that calls "EV::loop" (usually the main program) is not the
240 same module as a long-living watcher (for example a DNS client
241 module written by somebody else even). Then you might want any
242 outstanding requests to be handled, but you would not want to keep
243 "EV::loop" from returning just because you happen to have this
244 long-running UDP port watcher.
245
246 In this case you can clear the keepalive status, which means that
247 even though your watcher is active, it won't keep "EV::loop" from
248 returning.
249
250 The initial value for keepalive is true (enabled), and you cna
251 change it any time.
252
253 Example: Register an I/O watcher for some UDP socket but do not keep
254 the event loop from running just because of that watcher.
255
256 my $udp_socket = ...
257 my $udp_watcher = EV::io $udp_socket, EV::READ, sub { ... };
258 $udp_watcher->keepalive (0);
259
260 WATCHER TYPES
261 Each of the following subsections describes a single watcher type.
262
263 I/O WATCHERS - is this file descriptor readable or writable?
170 $w = EV::io $fileno_or_fh, $eventmask, $callback 264 $w = EV::io $fileno_or_fh, $eventmask, $callback
171 $w = EV::io_ns $fileno_or_fh, $eventmask, $callback 265 $w = EV::io_ns $fileno_or_fh, $eventmask, $callback
172 As long as the returned watcher object is alive, call the $callback 266 As long as the returned watcher object is alive, call the $callback
173 when the events specified in $eventmask. 267 when at least one of events specified in $eventmask occurs.
174 268
175 The $eventmask can be one or more of these constants ORed together: 269 The $eventmask can be one or more of these constants ORed together:
176 270
177 EV::READ wait until read() wouldn't block anymore 271 EV::READ wait until read() wouldn't block anymore
178 EV::WRITE wait until write() wouldn't block anymore 272 EV::WRITE wait until write() wouldn't block anymore
… …
190 284
191 $current_eventmask = $w->events 285 $current_eventmask = $w->events
192 $old_eventmask = $w->events ($new_eventmask) 286 $old_eventmask = $w->events ($new_eventmask)
193 Returns the previously set event mask and optionally set a new one. 287 Returns the previously set event mask and optionally set a new one.
194 288
289 TIMER WATCHERS - relative and optionally repeating timeouts
195 $w = EV::timer $after, $repeat, $callback 290 $w = EV::timer $after, $repeat, $callback
196 $w = EV::timer_ns $after, $repeat, $callback 291 $w = EV::timer_ns $after, $repeat, $callback
197 Calls the callback after $after seconds. If $repeat is non-zero, the 292 Calls the callback after $after seconds (which may be fractional).
198 timer will be restarted (with the $repeat value as $after) after the 293 If $repeat is non-zero, the timer will be restarted (with the
199 callback returns. 294 $repeat value as $after) after the callback returns.
200 295
201 This means that the callback would be called roughly after $after 296 This means that the callback would be called roughly after $after
202 seconds, and then every $repeat seconds. "Roughly" because the time 297 seconds, and then every $repeat seconds. The timer does his best not
203 of callback processing is not taken into account, so the timer will 298 to drift, but it will not invoke the timer more often then once per
204 slowly drift. If that isn't acceptable, look at EV::periodic. 299 event loop iteration, and might drift in other cases. If that isn't
300 acceptable, look at EV::periodic, which can provide long-term stable
301 timers.
205 302
206 The timer is based on a monotonic clock, that is if somebody is 303 The timer is based on a monotonic clock, that is, if somebody is
207 sitting in front of the machine while the timer is running and 304 sitting in front of the machine while the timer is running and
208 changes the system clock, the timer will nevertheless run (roughly) 305 changes the system clock, the timer will nevertheless run (roughly)
209 the same time. 306 the same time.
210 307
211 The "timer_ns" variant doesn't start (activate) the newly created 308 The "timer_ns" variant doesn't start (activate) the newly created
212 watcher. 309 watcher.
213 310
214 $w->set ($after, $repeat) 311 $w->set ($after, $repeat)
215 Reconfigures the watcher, see the constructor above for details. Can 312 Reconfigures the watcher, see the constructor above for details. Can
216 be at any time. 313 be called at any time.
217 314
218 $w->again 315 $w->again
219 Similar to the "start" method, but has special semantics for 316 Similar to the "start" method, but has special semantics for
220 repeating timers: 317 repeating timers:
221 318
319 If the timer is active and non-repeating, it will be stopped.
320
222 If the timer is active and repeating, reset the timeout to occur 321 If the timer is active and repeating, reset the timeout to occur
223 $repeat seconds after now. 322 $repeat seconds after now.
224 323
225 If the timer is active and non-repeating, it will be stopped.
226
227 If the timer is in active and repeating, start it. 324 If the timer is inactive and repeating, start it using the repeat
325 value.
228 326
229 Otherwise do nothing. 327 Otherwise do nothing.
230 328
231 This behaviour is useful when you have a timeout for some IO 329 This behaviour is useful when you have a timeout for some IO
232 operation. You create a timer object with the same value for $after 330 operation. You create a timer object with the same value for $after
233 and $repeat, and then, in the read/write watcher, run the "again" 331 and $repeat, and then, in the read/write watcher, run the "again"
234 method on the timeout. 332 method on the timeout.
235 333
334 PERIODIC WATCHERS - to cron or not to cron?
236 $w = EV::periodic $at, $interval, $callback 335 $w = EV::periodic $at, $interval, $reschedule_cb, $callback
237 $w = EV::periodic_ns $at, $interval, $callback 336 $w = EV::periodic_ns $at, $interval, $reschedule_cb, $callback
238 Similar to EV::timer, but the time is given as an absolute point in 337 Similar to EV::timer, but is not based on relative timeouts but on
239 time ($at), plus an optional $interval. 338 absolute times. Apart from creating "simple" timers that trigger
339 "at" the specified time, it can also be used for non-drifting
340 absolute timers and more complex, cron-like, setups that are not
341 adversely affected by time jumps (i.e. when the system clock is
342 changed by explicit date -s or other means such as ntpd). It is also
343 the most complex watcher type in EV.
240 344
241 If the $interval is zero, then the callback will be called at the 345 It has three distinct "modes":
242 time $at if that is in the future, or as soon as possible if it is
243 in the past. It will not automatically repeat.
244 346
245 If the $interval is nonzero, then the watcher will always be 347 * absolute timer ($interval = $reschedule_cb = 0)
246 scheduled to time out at the next "$at + N * $interval" time. 348 This time simply fires at the wallclock time $at and doesn't
349 repeat. It will not adjust when a time jump occurs, that is, if
350 it is to be run at January 1st 2011 then it will run when the
351 system time reaches or surpasses this time.
247 352
248 This can be used to schedule a callback to run at very regular 353 * non-repeating interval timer ($interval > 0, $reschedule_cb = 0)
249 intervals, as long as the processing time is less then the interval 354 In this mode the watcher will always be scheduled to time out at
250 (otherwise obviously events will be skipped). 355 the next "$at + N * $interval" time (for some integer N) and
356 then repeat, regardless of any time jumps.
251 357
358 This can be used to create timers that do not drift with respect
359 to system time:
360
361 my $hourly = EV::periodic 0, 3600, 0, sub { print "once/hour\n" };
362
363 That doesn't mean there will always be 3600 seconds in between
364 triggers, but only that the the clalback will be called when the
365 system time shows a full hour (UTC).
366
252 Another way to think about it (for the mathematically inclined) is 367 Another way to think about it (for the mathematically inclined)
253 that EV::periodic will try to run the callback at the next possible 368 is that EV::periodic will try to run the callback in this mode
254 time where "$time = $at (mod $interval)", regardless of any time 369 at the next possible time where "$time = $at (mod $interval)",
255 jumps. 370 regardless of any time jumps.
256 371
257 This periodic timer is based on "wallclock time", that is, if the 372 * manual reschedule mode ($reschedule_cb = coderef)
258 clock changes ("ntp", "date -s" etc.), then the timer will 373 In this mode $interval and $at are both being ignored. Instead,
259 nevertheless run at the specified time. This means it will never 374 each time the periodic watcher gets scheduled, the reschedule
260 drift (it might jitter, but it will not drift). 375 callback ($reschedule_cb) will be called with the watcher as
376 first, and the current time as second argument.
377
378 *This callback MUST NOT stop or destroy this or any other
379 periodic watcher, ever*. If you need to stop it, return 1e30 and
380 stop it afterwards.
381
382 It must return the next time to trigger, based on the passed
383 time value (that is, the lowest time value larger than to the
384 second argument). It will usually be called just before the
385 callback will be triggered, but might be called at other times,
386 too.
387
388 This can be used to create very complex timers, such as a timer
389 that triggers on each midnight, local time (actually 24 hours
390 after the last midnight, to keep the example simple. If you know
391 a way to do it correctly in about the same space (without
392 requiring elaborate modules), drop me a note :):
393
394 my $daily = EV::periodic 0, 0, sub {
395 my ($w, $now) = @_;
396
397 use Time::Local ();
398 my (undef, undef, undef, $d, $m, $y) = localtime $now;
399 86400 + Time::Local::timelocal 0, 0, 0, $d, $m, $y
400 }, sub {
401 print "it's midnight or likely shortly after, now\n";
402 };
261 403
262 The "periodic_ns" variant doesn't start (activate) the newly created 404 The "periodic_ns" variant doesn't start (activate) the newly created
263 watcher. 405 watcher.
264 406
265 $w->set ($at, $interval) 407 $w->set ($at, $interval, $reschedule_cb)
266 Reconfigures the watcher, see the constructor above for details. Can 408 Reconfigures the watcher, see the constructor above for details. Can
267 be at any time. 409 be called at any time.
268 410
411 $w->again
412 Simply stops and starts the watcher again.
413
414 SIGNAL WATCHERS - signal me when a signal gets signalled!
269 $w = EV::signal $signal, $callback 415 $w = EV::signal $signal, $callback
270 $w = EV::signal_ns $signal, $callback 416 $w = EV::signal_ns $signal, $callback
271 Call the callback when $signal is received (the signal can be 417 Call the callback when $signal is received (the signal can be
272 specified by number or by name, just as with kill or %SIG). 418 specified by number or by name, just as with "kill" or %SIG).
273 419
274 EV will grab the signal for the process (the kernel only allows one 420 EV will grab the signal for the process (the kernel only allows one
275 component to receive a signal at a time) when you start a signal 421 component to receive a signal at a time) when you start a signal
276 watcher, and removes it again when you stop it. Perl does the same 422 watcher, and removes it again when you stop it. Perl does the same
277 when you add/remove callbacks to %SIG, so watch out. 423 when you add/remove callbacks to %SIG, so watch out.
… …
281 The "signal_ns" variant doesn't start (activate) the newly created 427 The "signal_ns" variant doesn't start (activate) the newly created
282 watcher. 428 watcher.
283 429
284 $w->set ($signal) 430 $w->set ($signal)
285 Reconfigures the watcher, see the constructor above for details. Can 431 Reconfigures the watcher, see the constructor above for details. Can
286 be at any time. 432 be called at any time.
287 433
288 $current_signum = $w->signal 434 $current_signum = $w->signal
289 $old_signum = $w->signal ($new_signal) 435 $old_signum = $w->signal ($new_signal)
290 Returns the previously set signal (always as a number not name) and 436 Returns the previously set signal (always as a number not name) and
291 optionally set a new one. 437 optionally set a new one.
292 438
439 CHILD WATCHERS - watch out for process status changes
293 $w = EV::child $pid, $callback 440 $w = EV::child $pid, $callback
294 $w = EV::child_ns $pid, $callback 441 $w = EV::child_ns $pid, $callback
295 Call the callback when a status change for pid $pid (or any pid if 442 Call the callback when a status change for pid $pid (or any pid if
296 $pid is 0) has been received. More precisely: when the process 443 $pid is 0) has been received. More precisely: when the process
297 receives a SIGCHLD, EV will fetch the outstanding exit/wait status 444 receives a "SIGCHLD", EV will fetch the outstanding exit/wait status
298 for all changed/zombie children and call the callback. 445 for all changed/zombie children and call the callback.
299 446
300 You can access both status and pid by using the "rstatus" and "rpid" 447 It is valid (and fully supported) to install a child watcher after a
448 child has exited but before the event loop has started its next
449 iteration (for example, first you "fork", then the new child process
450 might exit, and only then do you install a child watcher in the
451 parent for the new pid).
452
453 You can access both exit (or tracing) status and pid by using the
301 methods on the watcher object. 454 "rstatus" and "rpid" methods on the watcher object.
302 455
303 You can have as many pid watchers per pid as you want. 456 You can have as many pid watchers per pid as you want, they will all
457 be called.
304 458
305 The "child_ns" variant doesn't start (activate) the newly created 459 The "child_ns" variant doesn't start (activate) the newly created
306 watcher. 460 watcher.
307 461
308 $w->set ($pid) 462 $w->set ($pid)
309 Reconfigures the watcher, see the constructor above for details. Can 463 Reconfigures the watcher, see the constructor above for details. Can
310 be at any time. 464 be called at any time.
311 465
312 $current_pid = $w->pid 466 $current_pid = $w->pid
313 $old_pid = $w->pid ($new_pid) 467 $old_pid = $w->pid ($new_pid)
314 Returns the previously set process id and optionally set a new one. 468 Returns the previously set process id and optionally set a new one.
315 469
… …
319 473
320 $pid = $w->rpid 474 $pid = $w->rpid
321 Return the pid of the awaited child (useful when you have installed 475 Return the pid of the awaited child (useful when you have installed
322 a watcher for all pids). 476 a watcher for all pids).
323 477
478 STAT WATCHERS - did the file attributes just change?
479 $w = EV::stat $path, $interval, $callback
480 $w = EV::stat_ns $path, $interval, $callback
481 Call the callback when a file status change has been detected on
482 $path. The $path does not need to exist, changing from "path exists"
483 to "path does not exist" is a status change like any other.
484
485 The $interval is a recommended polling interval for systems where
486 OS-supported change notifications don't exist or are not supported.
487 If you use 0 then an unspecified default is used (which is highly
488 recommended!), which is to be expected to be around five seconds
489 usually.
490
491 This watcher type is not meant for massive numbers of stat watchers,
492 as even with OS-supported change notifications, this can be
493 resource-intensive.
494
495 The "stat_ns" variant doesn't start (activate) the newly created
496 watcher.
497
498 ... = $w->stat
499 This call is very similar to the perl "stat" built-in: It stats
500 (using "lstat") the path specified in the watcher and sets perls
501 stat cache (as well as EV's idea of the current stat values) to the
502 values found.
503
504 In scalar context, a boolean is return indicating success or failure
505 of the stat. In list context, the same 13-value list as with stat is
506 returned (except that the blksize and blocks fields are not
507 reliable).
508
509 In the case of an error, errno is set to "ENOENT" (regardless of the
510 actual error value) and the "nlink" value is forced to zero (if the
511 stat was successful then nlink is guaranteed to be non-zero).
512
513 See also the next two entries for more info.
514
515 ... = $w->attr
516 Just like "$w->stat", but without the initial stat'ing: this returns
517 the values most recently detected by EV. See the next entry for more
518 info.
519
520 ... = $w->prev
521 Just like "$w->stat", but without the initial stat'ing: this returns
522 the previous set of values, before the change.
523
524 That is, when the watcher callback is invoked, "$w->prev" will be
525 set to the values found *before* a change was detected, while
526 "$w->attr" returns the values found leading to the change detection.
527 The difference (if any) between "prev" and "attr" is what triggered
528 the callback.
529
530 If you did something to the filesystem object and do not want to
531 trigger yet another change, you can call "stat" to update EV's idea
532 of what the current attributes are.
533
534 $w->set ($path, $interval)
535 Reconfigures the watcher, see the constructor above for details. Can
536 be called at any time.
537
538 $current_path = $w->path
539 $old_path = $w->path ($new_path)
540 Returns the previously set path and optionally set a new one.
541
542 $current_interval = $w->interval
543 $old_interval = $w->interval ($new_interval)
544 Returns the previously set interval and optionally set a new one.
545 Can be used to query the actual interval used.
546
547 IDLE WATCHERS - when you've got nothing better to do...
324 $w = EV::idle $callback 548 $w = EV::idle $callback
325 $w = EV::idle_ns $callback 549 $w = EV::idle_ns $callback
326 Call the callback when there are no pending io, timer/periodic, 550 Call the callback when there are no other pending watchers of the
327 signal or child events, i.e. when the process is idle. 551 same or higher priority (excluding check, prepare and other idle
552 watchers of the same or lower priority, of course). They are called
553 idle watchers because when the watcher is the highest priority
554 pending event in the process, the process is considered to be idle
555 at that priority.
556
557 If you want a watcher that is only ever called when *no* other
558 events are outstanding you have to set the priority to "EV::MINPRI".
328 559
329 The process will not block as long as any idle watchers are active, 560 The process will not block as long as any idle watchers are active,
330 and they will be called repeatedly until stopped. 561 and they will be called repeatedly until stopped.
331 562
563 For example, if you have idle watchers at priority 0 and 1, and an
564 I/O watcher at priority 0, then the idle watcher at priority 1 and
565 the I/O watcher will always run when ready. Only when the idle
566 watcher at priority 1 is stopped and the I/O watcher at priority 0
567 is not pending with the 0-priority idle watcher be invoked.
568
332 The "idle_ns" variant doesn't start (activate) the newly created 569 The "idle_ns" variant doesn't start (activate) the newly created
333 watcher. 570 watcher.
334 571
572 PREPARE WATCHERS - customise your event loop!
335 $w = EV::prepare $callback 573 $w = EV::prepare $callback
336 $w = EV::prepare_ns $callback 574 $w = EV::prepare_ns $callback
337 Call the callback just before the process would block. You can still 575 Call the callback just before the process would block. You can still
338 create/modify any watchers at this point. 576 create/modify any watchers at this point.
339 577
340 See the EV::check watcher, below, for explanations and an example. 578 See the EV::check watcher, below, for explanations and an example.
341 579
342 The "prepare_ns" variant doesn't start (activate) the newly created 580 The "prepare_ns" variant doesn't start (activate) the newly created
343 watcher. 581 watcher.
344 582
583 CHECK WATCHERS - customise your event loop even more!
345 $w = EV::check $callback 584 $w = EV::check $callback
346 $w = EV::check_ns $callback 585 $w = EV::check_ns $callback
347 Call the callback just after the process wakes up again (after it 586 Call the callback just after the process wakes up again (after it
348 has gathered events), but before any other callbacks have been 587 has gathered events), but before any other callbacks have been
349 invoked. 588 invoked.
… …
360 # do nothing unless active 599 # do nothing unless active
361 $dispatcher->{_event_queue_h} 600 $dispatcher->{_event_queue_h}
362 or return; 601 or return;
363 602
364 # make the dispatcher handle any outstanding stuff 603 # make the dispatcher handle any outstanding stuff
604 ... not shown
365 605
366 # create an IO watcher for each and every socket 606 # create an I/O watcher for each and every socket
367 @snmp_watcher = ( 607 @snmp_watcher = (
368 (map { EV::io $_, EV::READ, sub { } } 608 (map { EV::io $_, EV::READ, sub { } }
369 keys %{ $dispatcher->{_descriptors} }), 609 keys %{ $dispatcher->{_descriptors} }),
610
611 EV::timer +($event->[Net::SNMP::Dispatcher::_ACTIVE]
612 ? $event->[Net::SNMP::Dispatcher::_TIME] - EV::now : 0),
613 0, sub { },
370 ); 614 );
371
372 # if there are any timeouts, also create a timer
373 push @snmp_watcher, EV::timer $event->[Net::SNMP::Dispatcher::_TIME] - EV::now, 0, sub { }
374 if $event->[Net::SNMP::Dispatcher::_ACTIVE];
375 }; 615 };
376 616
377 The callbacks are irrelevant, the only purpose of those watchers is 617 The callbacks are irrelevant (and are not even being called), the
378 to wake up the process as soon as one of those events occurs (socket 618 only purpose of those watchers is to wake up the process as soon as
379 readable, or timer timed out). The corresponding EV::check watcher 619 one of those events occurs (socket readable, or timer timed out).
380 will then clean up: 620 The corresponding EV::check watcher will then clean up:
381 621
382 our $snmp_check = EV::check sub { 622 our $snmp_check = EV::check sub {
383 # destroy all watchers 623 # destroy all watchers
384 @snmp_watcher = (); 624 @snmp_watcher = ();
385 625
386 # make the dispatcher handle any new stuff 626 # make the dispatcher handle any new stuff
627 ... not shown
387 }; 628 };
388 629
389 The callbacks of the created watchers will not be called as the 630 The callbacks of the created watchers will not be called as the
390 watchers are destroyed before this cna happen (remember EV::check 631 watchers are destroyed before this cna happen (remember EV::check
391 gets called first). 632 gets called first).
392 633
393 The "check_ns" variant doesn't start (activate) the newly created 634 The "check_ns" variant doesn't start (activate) the newly created
394 watcher. 635 watcher.
395 636
637 FORK WATCHERS - the audacity to resume the event loop after a fork
638 Fork watchers are called when a "fork ()" was detected. The invocation
639 is done before the event loop blocks next and before "check" watchers
640 are being called, and only in the child after the fork.
641
642 $w = EV::fork $callback
643 $w = EV::fork_ns $callback
644 Call the callback before the event loop is resumed in the child
645 process after a fork.
646
647 The "fork_ns" variant doesn't start (activate) the newly created
648 watcher.
649
650PERL SIGNALS
651 While Perl signal handling (%SIG) is not affected by EV, the behaviour
652 with EV is as the same as any other C library: Perl-signals will only be
653 handled when Perl runs, which means your signal handler might be invoked
654 only the next time an event callback is invoked.
655
656 The solution is to use EV signal watchers (see "EV::signal"), which will
657 ensure proper operations with regards to other event watchers.
658
659 If you cannot do this for whatever reason, you can also force a watcher
660 to be called on every event loop iteration by installing a "EV::check"
661 watcher:
662
663 my $async_check = EV::check sub { };
664
665 This ensures that perl shortly gets into control for a short time, and
666 also ensures slower overall operation.
667
396THREADS 668THREADS
397 Threads are not supported by this in any way. Perl pseudo-threads is 669 Threads are not supported by this module in any way. Perl pseudo-threads
398 evil stuff and must die. 670 is evil stuff and must die. As soon as Perl gains real threads I will
671 work on thread support for it.
672
673FORK
674 Most of the "improved" event delivering mechanisms of modern operating
675 systems have quite a few problems with fork(2) (to put it bluntly: it is
676 not supported and usually destructive). Libev makes it possible to work
677 around this by having a function that recreates the kernel state after
678 fork in the child.
679
680 On non-win32 platforms, this module requires the pthread_atfork
681 functionality to do this automatically for you. This function is quite
682 buggy on most BSDs, though, so YMMV. The overhead for this is quite
683 negligible, because everything the function currently does is set a flag
684 that is checked only when the event loop gets used the next time, so
685 when you do fork but not use EV, the overhead is minimal.
686
687 On win32, there is no notion of fork so all this doesn't apply, of
688 course.
399 689
400SEE ALSO 690SEE ALSO
401 L<EV::DNS>, L<EV::AnyEvent>. 691 EV::ADNS (asynchronous dns), Glib::EV (makes Glib/Gtk2 use EV as event
692 loop), Coro::EV (efficient coroutines with EV).
402 693
403AUTHOR 694AUTHOR
404 Marc Lehmann <schmorp@schmorp.de> 695 Marc Lehmann <schmorp@schmorp.de>
405 http://home.schmorp.de/ 696 http://home.schmorp.de/
406 697

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